President Donald Trump, in transit to his historic summit with North Korean Dictator Kim Jong Un, tweeted that Larry Kudlow, his new chief economic adviser, has suffered a heart attack.

"Our Great Larry Kudlow, who has been working so hard on trade and the economy, has just suffered a heart attack".

Kudlow has been taken to Walter Reed Medical Center, the president said.

Senior White House economic adviser Larry Kudlow speaks during a briefing at the White House in Washington. The associates spoke on the condition of anonymity due to sensitives of Kudlow's health status. U.S. President Donald Trump says Kudlow suffered a heart attack on June 11.

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Kudlow has always been a respected business and economics commentator, getting his own CNBC show in 2011.

A longtime television commentator, Kudlow, 70, was hired by Trump in March to replace Gary Cohn as director of the National Economic Council.

Kudlow had worked as a White House budget aide in the Reagan administration, and had also been an informal advisor to the 2016 Trump campaign.

Kudlow joined the president at the Group of Seven summit in Quebec on Friday and Saturday.

Kudlow went on to label Trudeau's news conference, at which the prime minister said "Canadians will not be pushed around" on the issue of tariffs, as a "betrayal".